linux/arch/x86/kvm/vmx/posted_intr.h

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __KVM_X86_VMX_POSTED_INTR_H
#define __KVM_X86_VMX_POSTED_INTR_H
#define POSTED_INTR_ON 0
#define POSTED_INTR_SN 1
/* Posted-Interrupt Descriptor */
struct pi_desc {
u32 pir[8]; /* Posted interrupt requested */
union {
struct {
/* bit 256 - Outstanding Notification */
u16 on : 1,
/* bit 257 - Suppress Notification */
sn : 1,
/* bit 271:258 - Reserved */
rsvd_1 : 14;
/* bit 279:272 - Notification Vector */
u8 nv;
/* bit 287:280 - Reserved */
u8 rsvd_2;
/* bit 319:288 - Notification Destination */
u32 ndst;
};
u64 control;
};
u32 rsvd[6];
} __aligned(64);
static inline bool pi_test_and_set_on(struct pi_desc *pi_desc)
{
return test_and_set_bit(POSTED_INTR_ON,
(unsigned long *)&pi_desc->control);
}
static inline bool pi_test_and_clear_on(struct pi_desc *pi_desc)
{
return test_and_clear_bit(POSTED_INTR_ON,
(unsigned long *)&pi_desc->control);
}
KVM: VMX: Handle PI descriptor updates during vcpu_put/load Move the posted interrupt pre/post_block logic into vcpu_put/load respectively, using the kvm_vcpu_is_blocking() to determining whether or not the wakeup handler needs to be set (and unset). This avoids updating the PI descriptor if halt-polling is successful, reduces the number of touchpoints for updating the descriptor, and eliminates the confusing behavior of intentionally leaving a "stale" PI.NDST when a blocking vCPU is scheduled back in after preemption. The downside is that KVM will do the PID update twice if the vCPU is preempted after prepare_to_rcuwait() but before schedule(), but that's a rare case (and non-existent on !PREEMPT kernels). The notable wart is the need to send a self-IPI on the wakeup vector if an outstanding notification is pending after configuring the wakeup vector. Ideally, KVM would just do a kvm_vcpu_wake_up() in this case, but the scheduler doesn't support waking a task from its preemption notifier callback, i.e. while the task is right in the middle of being scheduled out. Note, setting the wakeup vector before halt-polling is not necessary: once the pending IRQ will be recorded in the PIR, kvm_vcpu_has_events() will detect this (via kvm_cpu_get_interrupt(), kvm_apic_get_interrupt(), apic_has_interrupt_for_ppr() and finally vmx_sync_pir_to_irr()) and terminate the polling. Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20211208015236.1616697-5-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-12-08 09:52:14 +08:00
static inline bool pi_test_and_clear_sn(struct pi_desc *pi_desc)
{
return test_and_clear_bit(POSTED_INTR_SN,
(unsigned long *)&pi_desc->control);
}
static inline bool pi_test_and_set_pir(int vector, struct pi_desc *pi_desc)
{
return test_and_set_bit(vector, (unsigned long *)pi_desc->pir);
}
static inline bool pi_is_pir_empty(struct pi_desc *pi_desc)
{
return bitmap_empty((unsigned long *)pi_desc->pir, NR_VECTORS);
}
static inline void pi_set_sn(struct pi_desc *pi_desc)
{
set_bit(POSTED_INTR_SN,
(unsigned long *)&pi_desc->control);
}
static inline void pi_set_on(struct pi_desc *pi_desc)
{
set_bit(POSTED_INTR_ON,
(unsigned long *)&pi_desc->control);
}
static inline void pi_clear_on(struct pi_desc *pi_desc)
{
clear_bit(POSTED_INTR_ON,
(unsigned long *)&pi_desc->control);
}
static inline void pi_clear_sn(struct pi_desc *pi_desc)
{
clear_bit(POSTED_INTR_SN,
(unsigned long *)&pi_desc->control);
}
static inline bool pi_test_on(struct pi_desc *pi_desc)
{
return test_bit(POSTED_INTR_ON,
(unsigned long *)&pi_desc->control);
}
static inline bool pi_test_sn(struct pi_desc *pi_desc)
{
return test_bit(POSTED_INTR_SN,
(unsigned long *)&pi_desc->control);
}
void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu);
void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu);
void pi_wakeup_handler(void);
void __init pi_init_cpu(int cpu);
bool pi_has_pending_interrupt(struct kvm_vcpu *vcpu);
int pi_update_irte(struct kvm *kvm, unsigned int host_irq, uint32_t guest_irq,
bool set);
KVM: VMX: update vcpu posted-interrupt descriptor when assigning device For VMX, when a vcpu enters HLT emulation, pi_post_block will: 1) Add vcpu to per-cpu list of blocked vcpus. 2) Program the posted-interrupt descriptor "notification vector" to POSTED_INTR_WAKEUP_VECTOR With interrupt remapping, an interrupt will set the PIR bit for the vector programmed for the device on the CPU, test-and-set the ON bit on the posted interrupt descriptor, and if the ON bit is clear generate an interrupt for the notification vector. This way, the target CPU wakes upon a device interrupt and wakes up the target vcpu. Problem is that pi_post_block only programs the notification vector if kvm_arch_has_assigned_device() is true. Its possible for the following to happen: 1) vcpu V HLTs on pcpu P, kvm_arch_has_assigned_device is false, notification vector is not programmed 2) device is assigned to VM 3) device interrupts vcpu V, sets ON bit (notification vector not programmed, so pcpu P remains in idle) 4) vcpu 0 IPIs vcpu V (in guest), but since pi descriptor ON bit is set, kvm_vcpu_kick is skipped 5) vcpu 0 busy spins on vcpu V's response for several seconds, until RCU watchdog NMIs all vCPUs. To fix this, use the start_assignment kvm_x86_ops callback to kick vcpus out of the halt loop, so the notification vector is properly reprogrammed to the wakeup vector. Reported-by: Pei Zhang <pezhang@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Message-Id: <20210526172014.GA29007@fuller.cnet> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-27 01:20:14 +08:00
void vmx_pi_start_assignment(struct kvm *kvm);
#endif /* __KVM_X86_VMX_POSTED_INTR_H */